518 THE OUTGO OF ENERGY 



stroke cannot all escape by the resistance during 

 the stroke and the succeeding interval. The 

 next stroke comes before the outflow from the 

 preceding stroke is finished, and the stream be- 

 comes remittent. 



Still further increase the frequency of the 

 stroke. A rate will be reached at which one- 

 half the quantity received from the pump will 

 pass by the resistance during the stroke of the 

 pump and the remaining half will pass in the 

 interval between that stroke and the next ; 

 the intermittent will be converted into a con- 

 tinuous flow. 



Observe that the duration of the intervals is 

 greater than the duration of the strokes of the 

 pump. Thus the time during which the circula- 

 tion is carried on by the energy stored by the 

 pump in the elastic walls of the vessel is greater 

 than the time during which it is carried on by 

 the direct stroke of the pump. 



Note that the arterial pressure remains low 

 even after the stream becomes continuous. An 

 increase in the frequency of the beat has little 

 influence on the blood pressure where the peri- 

 pheral resistance is very slight. 



3. Close the side branch, so that the liquid 

 must pass through a high peripheral resistance. 

 Compress the bulb at such a rate that the outflow 

 shall be continuous. 



